Printing Transparency

Transparency is the visual interaction of objects which have differing degrees of opacity. As we explored in Chapter 39, InDesign lets you make objects transparent, and you can import transparent graphics from Illustrator, Photoshop and Acrobat. This gives you some design and production capabilities far beyond what you can create in QuarkXPress or PageMaker. However, you must consider some important consequences of using transparency when printing. The foremost of these is flattening.

Transparency Must Be Flattened

When it comes time to print, the beautiful transparent effects that you’ve created must be sent to a machine which doesn’t know what transparency is. PostScript—the language spoken by most laser printers, imagesetters, and platesetters—only understands objects which are completely opaque. So InDesign (or any application which works natively with transparency) must take the transparent objects and break them into lots of different non-transparent pieces; this process is called flattening. The result is a single opaque page that comes out of the printer.